Yes, yeast can use oxygen. In fact, yeast can thrive both in the presence and absence of oxygen.
Aerobic Respiration (With Oxygen)
When oxygen is available, yeast utilizes a process called aerobic respiration. This process is highly efficient in converting sugars (carbohydrates) into energy. The byproducts of aerobic respiration are:
- Carbon dioxide (CO2)
- Water (H2O)
This is why, for example, yeast is used in baking – the carbon dioxide produced makes the dough rise.
Anaerobic Respiration (Without Oxygen)
However, yeast also has the remarkable ability to survive and function without oxygen. This process is called anaerobic respiration, or fermentation. During fermentation, yeast converts sugars into:
- Ethanol (alcohol)
- Carbon dioxide (CO2)
This is the process used in brewing beer and making wine. The ethanol is the alcohol content of the beverage. The carbon dioxide contributes to carbonation (like in sparkling wine).
Summary
Yeast is a facultative anaerobe, meaning it can switch between aerobic and anaerobic respiration depending on the availability of oxygen. While aerobic respiration is more efficient, the ability to ferment allows yeast to survive and be useful in a variety of applications even in the absence of oxygen.
